1. Field of the Invention
The present invention relates to computer aided design (CAD) systems and computerized drafting tools for designing and modeling parts, such as sheet metal parts. More particularly, the invention relates to an apparatus and method for selecting, displaying and repositioning dimensions of a CAD part model on a display screen.
2. Background Information
Traditionally, the production of bent sheet metal components at, for example, a progressive sheet metal manufacturing facility, involves a series of production and manufacturing stages. The first stage is a design stage during which a sheet metal part design is developed based on a customer's specifications. The customer will typically place an order for a particular sheet metal component to be produced at the facility. The customer's order will usually include the necessary product and design information so that the factory may manufacture the component. This information may include, for example, the geometric dimensions of the part, the material required for the part (e.g., steel, stainless steel or aluminum), special forming information, the batch size, the delivery date, etc. The sheet metal part requested by the customer may be designed and produced for a wide variety of applications. For example, the produced component may ultimately be used as an outer casing for a computer, an electrical switchboard, an arm rest in an airplane, or a part of a door panel for a car.
During the design stage, the design office of the manufacturing facility may develop a sheet metal part design using an appropriate Computer Aided Design (CAD) system. Based on the customer's specifications, the CAD system may be utilized to develop a two-dimensional (2-D) model of the sheet metal part. Typically, the customer will provide a blueprint containing one or more drawings of the component and the critical geometric dimensions of the part. The dimensions are used to quantitatively describe the part geometry. The blueprint may also indicate any special formings or markings to be included in the part, such as the location of holes or other types of openings on the surface(s) of the sheet metal part. A CAD system operator will often use this blueprint to develop a 2-D model on the CAD system. The 2-D model may include a view of the flat sheet metal part that will be folded into the finished 3-D part, and one or more other orthographic views of the sheet metal part displaying bend line and/or dimensional information.
In recent years, the use and development of 2-D and three-dimensional (3-D) modeling in commercially available CAD/Computer Aided Manufacturing (CAM) systems have facilitated the process of modeling bent sheet metal components. The CAD system operator and part designer can now utilize both the 2-D and 3-D representations to better understand the geometry of the part and more efficiently develop a part design. In particular, the relationships between certain locations of the part that are significant (for exampele, because the part must fit into a defined location or space according to a specified orientation) may now be modeled and analyzed. Thus, the use of 2-D and 3-D modeling has reduced the time and effort required to analyze a part and determine whether the dimensions of the part will permit the part to fit into defined locations or environments. Prior to computer modeling, the part was physically measured after bending and then rebent if the part did not meet the specifications, resulting in a time consuming trial and error process for obtaining an optimal design.
Until now, modeling programs had limited capabilities because they only displayed predetermined dimensions of a part. In other words, the distances between certain predetermined entities (i.e., bend lines, faces, arcs and lines (edges) of the part) were automatically displayed. However, these automatic dimensions may not be the critical dimensions of the part or may not have even existed before the part was folded. Moreover, automatically displaying dimensions, typically causes too many dimensions to be displayed on the screen, causing a cluttered screen. Clutter occurs because automatic dimensions are an all or nothing proposition, i.e., either all of the dimensions are displayed or none are displayed. Thus, there is a need for tools which allow the user to decide which dimensions of a part are important, and select those dimensions for calculating and displaying. An additional need exists for allowing a user to prioritize the important dimensions for display and/or reposition the dimensions so that the screen does not appear cluttered. It follows, that when a user selects and prioritizes dimensions to display, time and effort goes into the selection. Consequently, a need exists for saving these dimensions in association with the part to capture the user's knowledge about the part.
A further need exists for selecting desired entities of a part from which to measure the dimension, without requiring tedious mouse manipulation. Typically, most of the prior systems use 2-D models or 3-D paper models, i.e., models without thickness. However, in the real world, parts have thickness. Consequently, when a part is bent, the thickness comes into play and affects dimensions. Thus, a need exists for selecting which side of the metal thickness, (i.e., the far or close side), the dimension is to be measured from. Furthermore, a need also exists to permit easily selecting a desired entity, especially when a multitude of entities exist.